Manufacture of high grade sodium cyanide



June 2l', 1938. J. CHRISTMANN 2,121,020

MANUFACTURE OF HIGH 4GRADE SODIUM CYANIDE Filed March lO, 1936 Patented June 2l, 1938 UNiTED ASTAT MANUFACTURE oF HIGH GRADE soniUM CYANIDE Ludwig J. Christmann, Jersey City, N. J., .assignor ,to American Cyanamid Company, New York,

N. Y., a corporation of Maine Application March 1o, 1936, serial No. 68,005

is claims.

The present invention relates to a cyclic method of preparing an alkali cyanide iny solid form out the necessity of passing it through an orating stage.

The principal obj terial may be reconditioned automatically,

ect of the invention is the preparation oi an alkali cyanide, preferably an alkali metal cyanide by cyclic methods whereby o a reagent used in the preparation of the ma- The. following is given as a specic example: 500 cc. of 1:1 caustic soda solution containing 376 gms. of caustic soda was neutralized with 249 gms.y of hydrocyanic acid. To this solution, heated to 40 C. 1473 cc. of anhydrous ethyl alco- 5 hol atthe 'same temperaturewas added. The precipitated crystals of sodium cyanide were then ltered from the menstruum, and dried in a vacuum oven at 72 C. land recovered. 'Ihe ltrate .was found to be principally aqueous ethyl alcohol Withevapmakl0 ing unnecessary further additions thereof to the cycle except Within very narrow limits. With a small percent of residual `sodium cyanide. To this end, .the invention contemplates the 500 cc. of this aqueous alcohol mixture Was then neutralization of a concentrated solution of alkali mixed with 150 grams of solid caustic soda withv hydroxide with hydrocyanic acid to form the agitation whereupon the alcohol was dehydrated desired cyanide in solution. To this mixture, a to a substantial extent. The caustic soda. solu- 15 water miscible liquid is then added in which the tion and the aqueous alcohol stratified, permitcyanide is insoluble or substantially so, resulting ting reasonable separation. The cycle was then in the precipitation of the cyanide in solid form. repeated, 'I'he cyanide may then be separated from the From the above, it will be noted that a cyclic liquid and to thf` 1atter Solid alkali hydroxide system for the production of an alkali metalcya- 20 added. Il'iis addition -causes areconditioning of Hide, has been proposed which does not involve ghe tprecllltatmg ltlfufldd mg' lmultanefus prio' evaporation of that solid from a water solution.

fue lon o conce. la e a al hydroxlde 50.11' The difficulties attending such Arecovery are,

lon. The cycle 1s then repeated. The detailed 1 h 1 u d process is shown in the flow Sheet l therefore, avoided. The anhydrous aco o. se 25 Referring to this diagrammatic showing, it will to pt eciptate 50nd alkah niet@ Cyamdef, ls re' be seen that it; is first, proposed to prepare a conditioned by means of additional quantities of concentrated solution of caustic soda in water. Solid Caustic going back 111'00 the System all 0f This should preferably bea 1:1 solution. Hywhich makes for a smooth working, efficient sysdrocyanic acid is then added eitherin liquid tem. Alkali metal cyanide Crystals 0f the Order or gaseous form until neutralization has been of 97% purity have been recovered' rby this effected. The sodium cyanide in solution is then method. precipitated by adding requisite quantities of a I claim:

y vsubstantially anhydrous water miscible liquid, 1. A cyclic method of preparing an alkali metal 3D of which ethyl, isopropyl and tertiary butyl alCO- cyanide in solid form which comprises neutral- 35 hols are examples.

entry into the cycle. ical water which would otherwise build able point in the cycle.

While any substantially anhydrous water miscible liquid in' which the cyanide is substantially vinsoluble may be used, yet the above are preferred because of their greater efliciency. The solid cyanide is separated from the aqueous alcohol as by filtering or the like, suitably dried to remove residual alcohol and briquetted or not as desired. The aqueous alcohol is then mixed with an additional quantity of solid caustic soda, with the consequent production of concentrated caustic soda solution and substantially anhydrous alcohol, the caustic soda serving to recondition the alcohol for re- Where desired, the chemizing HCN with a concentrated solution of an alkali metal hydroxide, thus forming an alkali metal cyanide in solution, adding to the reaction material a water miscible liquid contadining only a small quantity of water, in :which 4 the alkali metal cyanide is substantially insoluble, in an amount sufficient to precipitate substantially all of the alkali metal cyanide, separating the aqueous liquid and the cyanide and recovering the latter, treating the aqueous liquid with sufficient solid alkali metal hydroxide to cause some dehydration oi" the water miscible liquid and separation of the total liquid into two phases, one a solution of alkali metal hydroxide, and the other predominantly the water miscible liquid and using kthe rhydroxide solution to neutralize additional quantities of I-ICN, and the partially dehydrated water miscible liquid to precipitate out the thus formed alkali metal cyanide.

up in 2. The method of claim 1 in which the hydroxide is of sodium.

3. The method of claim 1 in Which the HCN is in liquid form. y

4. The method of claim 1 in which the hydroxide initially used is substantially a 1:1 solution.

5. The method of claim 1 in which the separation of the hydroxide solution from the Water miscible liquid is accomplished by stratication.

6. The method of claim 1 in which the cyanide is precipitated from solution at substantially 40 C.

'7. The method of claim 1 With the additional step of removing the excess Water from the system.

8. 'Ihe method of claim 1 using sodium hydroxide as a 1:1 solution with the additional step of removing the excess Water from the system.

9. The method of claim 1in which the Water miscible liquid is an alcohol.

10. The method of claim 1 in Which the Water miscible liquid is chosen from the group comprising ethyl, isopropyl and tertiary butyl alcohols.

11. The method of claim 1 in which the Water miscible liquid is ethyl alcohol.

12. The method of claim 1 in which the Water miscible liquid is isopropyl alcohol.

13. The method of claim 1 in which the Water miscible liquid is tertiary butyl alcohol.

LUDWIG J. CHRISTMANN. 

